This project focuses in large part on structure-function-mechanism aspects of the transfer RNAs and their interactions with specific proteins. Particular attention is directed at the molecular basis for specificity in complexes of the transfer RNAs with aminoacyl transfer RNA synthetases and with the elongation factor Tu. These problems have been and/or are being attacked with a photo-chemical crosslinking procedure and isotope labeling approach. In addition, photo-crosslinked synthetase-ATP complexes are being investigated; the amino acid sequence of peptide(s) attached to ATP is to be determined for two or more synthetases. In this way, the possibility of sequence homologies at the ATP sites of various synthetases may be tested. Finally, affinity columns containing specific transfer RNAs are to be constructed with the hope of isolating as yet undiscovered proteins that bind to specific transfer RNA species.